23 Multiple choice questions
- Variable names are case-sensitive. So, for example,$This_Variable is not the same as $this_variable.
- To convert one variable type to another, reference it and PHP will automatically convert it for you.
- You can use \' or \" to escape either a single or double quote.
hyphen is reserved for the subtraction operators. A construct like
$current-user would be harder to interpret if hyphens were also allowed
in variable names and, in any case, would lead programs to be ambiguous.
are provided by the PHP environment but are global within the program,
accessible absolutely everywhere. All of the superglobals (except for
$GLOBALS) are named with a single initial underscore and only capital
- Variables hold a value that can be a string, a number, or other data.
the operators && and and are interchangeable except where
precedence is important, in which case && has a high precedence,
while and has a low one.
= 1 is an assignment statement, whereas $variable == 1 is a comparison
operator. Use $variable = 1 to set the value of $variable. Use $variable
== 1 to find out later in the program whether $variable equals 1. If
you mistakenly use $variable = 1 where you meant to do a comparison, it
will do two things you probably don't want: set $variable to 1 and
return a true value all the time, no matter what its previous value was.
the htmlentities function for sanitization is an important practice in
any circumstance where user or other third-party data is being processed
for output, not just with superglobals.
- With the exception of constants, all PHP variables must begin with $.
- When you combine a string with a number, the result is another string.
purpose of functions is to separate discrete sections of code into
their own, self-contained sections that can be referenced by a single
tag used to start PHP interpreting code is <?php ... ?>, which
can be shortened to <? ... ?> but is not recommended practice.
- You cannot use spaces in variable names, as this would confuse the PHP parser. Instead, try using the _ (underscore).
can use multiple lines within quotations marks or the <<<_END
... _END; construct to create a multiline echo or assignment. The
closing tag must begin at the start of a line, and end with a semicolon
followed by a new line.
- You cannot redefine constants because, by definition, once defined they retain their value until the program terminates.
echo and print commands are similar in that they are both constructs,
except that print behaves like a PHP function and takes a single
argument, while echo can take multiple arguments.
is no difference between ++$j and $j++ unless the value of $j is being
tested, assigned to another variable, or passed as a parameter to a
function. In such cases, ++$j increments $j before the test or other
operation is performed, whereas $j++ performs the operation and then
- All PHP statements must end with a semicolon (;).
you generate data within a function, you can convey the data to the
rest of the program by returning a value or modifying a global variable.
- You can use // for a single-line comment or / ... / to span multiple lines.
never reset and are only within the scope of the function. You cannot
assign the result of an expression in their definitions.
- You can make a variable accessible to all parts of a PHP program by declaring it as global.